The importance of harvesting renewable energy continues to grow along with the concerns over carbon emissions and the threat of serious climate change resulting from fossil fuelled power generation and transport. An important contributor to the mix of renewable energy sources is that of wind energy which has led to the development of increasingly efficient and larger wind energy generators.
Large tower-mounted, three-bladed horizontal axis wind turbine power generators however, are only suitable for rural installations. Numerous attempts have been made to develop and improve the efficiency of more compact vertical axis machines which more readily lend themselves to urban installations, being particularly suitable for fluctuating, turbulent wind conditions.
Output of VAWT machines can be significantly improved if the pitch of the blades can be optimised relative to the range of wind velocity at which maximum energy extraction is possible. Control is complicated by the varying loads placed on the blades as they present at varying angles to the wind during rotation, inducing a tendency to “oscillate” with attendant vibration, noise and wear. Additionally, the system must be able to withstand high winds and still maintain peak power output, while not allow the speed of rotation to exceed that which can be accommodated within the mechanical constraints of the turbine structure, transmission and electrical generator.
It is an object of the present invention to address or at least ameliorate some of the above problems.